1. Field of the Invention
The present invention relates to a system and method for determining an air purifier filter change time using a measurement of a motor speed and, more particularly, to a system and method for changing an air purifier filter provided in an air purifier at a proper time by measuring the rotational speed of the motor that operates the filter.
2. Description of the Related Art
In general, an air purifier is a device for purifying indoor air by removing dust and germs included in indoor air or deodorizing tobacco smoke, the smell of sweat, or the like.
Air purifiers generally suck in contaminated air through the action of a fan, collect and remove fine dust particles or germs of up to 0.03 μm by means of a filter and generate anions that have been reduced due to contaminated indoor air in order to provide an agreeable indoor environment.
FIG. 1 is a schematic block diagram of a motor driving system provided in the related art air purifier. As shown in FIG. 1, a power supply unit 20 is formed as a switching mode power supply (SMPS) or the like to convert an AC voltage, commercial power, into a DC voltage. A switching element driving unit 40 generates a switching control signal upon receiving the DC voltage which has been converted by the power supply unit 20. A switching element 50 converts the DC voltage applied from the power supply unit 20 into a three-phase voltage according to a switching control signal, and applies the converted voltage to a motor 10.
A coil (not shown) of the motor 10 generates a magnetic field by the three-phase voltage to rotate a rotor (not shown) of the motor 10. As the rotor of the motor 10 is rotated, a compressor (not shown) is driven.
A counter-electromotive force is output to the coil according to the rotation of the rotor of the motor 10, and a counter-electromotive force detection unit 70 detects the counter-electromotive force and applies it to a microcomputer 60. Upon detecting the counter-electromotive force, the microcomputer 60 controls the switching element driving unit 40 to allow the motor 10 to be accurately operated.
The DC voltage which has been converted by the power supply unit 20 is supplied to a high voltage generation unit 30. Then, the high voltage generation unit 30 generates a high voltage, and a dust collecting filter 80 collects dust by using the high voltage input from the high voltage generation unit 30. The DC voltage which has been converted by the power supply unit 20 is supplied to the microcomputer 60. Upon receiving the DC voltage, the microcomputer 60 performs functions such as air volume adjustment (or airflow adjustment), displaying degree of air contamination, timer correction, anion generation, and the like. An anion generation unit 90 induces a negative (−) high voltage together with the high voltage generation unit 30 and supplies the corresponding output to an anion generating needle to discharge anions.
The voltage applied to the motor 10 has a pulse width modulation (PWM) waveform, and if its duty ratio is high, the driving force of the motor 10 becomes stronger, whereas if the duty ratio is low, the driving force of the motor 10 is weak. A driving circuit of the motor 10 adjusts the rotational speed of the motor 10 by adjusting the duty ratio of the PWM, and the motor 10 rotates the fan.
In using the related art air purifier, if the degree of filter contamination is high, the time duration during which the air purifier has been used is totaled, in order to determine when it is necessary to change the filter.
Thus, in the related art, an accurate degree of filter contamination cannot be determined, causing a problem in that the filter is unnecessarily changed, even if there is a lesser degree of filter contamination from a predetermined amount deemed necessary to warrant a filter change. Namely, even when filter's degree of contamination is lower than the predetermined unacceptable degree of filter contamination, the filter is changed unnecessarily, and in the case the degree of filter contamination is higher than the predetermined unacceptable degree of filter contamination, the filter is not changed, resulting in a situation whereby the filter cannot operate properly.